Heating roller assembly



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United States Patent 3,414,711 HEATING ROLLER ASSEMBLY Louis Guyet, Colmar, and Jacques Menault, Venissieux,

France, assignors to Crylor, Paris, France, a French body corporate Filed Mar. 21, 1966, Ser. No. 535,973 Claims priority, application France, Mar. 22, 1965, 10,206 4 Claims. (Cl. 219-469) ABSTRACT OF THE DISCLOSURE The present invention relates to a heating roller assembly, for example for use in the heat treatment, at a definite temperature, of filamentary or flat articles, such as fibres or fabrics.

In the textile industry it is usual to pass fibres over rotating rollers which have to 'be heated. It is furthermore often necessary for the temperature of such rollers to be precisely controlled. In effect, a slight variation in the temperature of the heat treatment may in some cases result in unacceptable variations in the properties of the treated fibres.

It has been proposed to use a hollow rotating unit in the form of a solid of revolution, heated by radiation from a fixed element located inside the rotating unit. However the control of the temperature of the rotating unit in a device of this type has up to now never been solved satisfactorily. It has for example been suggested to use conducting sole-plates in order to bring the thermo metric sensing device to the same temperature as the rotating unit. The construction and use of such a device is especially complicated by the friction problems inherent in its operation.

It has also been suggested to use a rotating unit having the shape of a solid of revolution, heated by currents induced in the said unit, with a thermistor cast into the rotating unit providing the heating control. However such a device is very complicated and expensive. The induction heating is, in effect, difficult to employ because it causes a considerable lowering of the power factor. Furthermore, the currents used for control are low and their transmission by means of rotating sleeves is not perfect, and this can be the cause of defects in control. Furthermore, the number of contact devices becomes prohibitive if it is intended to have several temperature zones in the rotating unit. 60

According to the present invention we provide a heating roller assembly comprising a hollow cover, rotatable about an axis the cover having an internal surface whose total emission factor is close to that of a black body, a fixed element located inside the cover and having facing the internal surface of the cover, firstly a heating element surface whose total emission factor is close to that of a black body, and secondly a temperature sensing device "ice which is sensitive to heat radiation, adapted to control the heating of said heating surface and located outside the said heating surface and thermally insulated therefrom.

The form of the external surface of the cover varies according to the use to be made of this unit; and is generally cylindrical, but may be more complex. In order to avoid heat losses it is desirable that the cover should be externally polished. The heat inertia of the cover is advantageously reduced by making it as thin as possible.

The internal surface of the cover may be naturally black, or it may be covered with a lining which gives it a total emission factor close to that of a black body at the use temperature envisaged. Such a lining may for example consist of matt black commercially available paints, or of nickel black, silver black or gold black obtained by vaporisation of the corresponding metal in a high vacuum. The total emission factor of these linings reaches, or exceeds, 0.90 at the use temperatures envisaged.

The heating element advantageously consists of an electrical resistance, but it is possible to use other devices such as a pipeline in which a heated liquid circulates. The heating element is advantageously cast in a metal such as bronze or brass, so as to have as high an emission surface as possible. The external surface of the heating element, facing the internal surface of the rotating unit, has a total emission factor close to that of a black body, this being obtained either by imparting a striated appearance to this surface or by covering this surface with a coating having properties close to those of a black body, for example commercially available paints, nickel black, silver black or gold black, or by using the two methods conjointly. Preferably, the external surface of the heating element comprises the greater part of the external surface of the fixed element facing the internal surface of the rotating unit.

The temperature sensing device is integral with the fixed element and is thermally insulated from the heating part of this element "by an insulating material, for example asbestos, refractory cement, or diatomaceous earth agglomerates. According to a preferred embodiment, one uses a thermistor fixed facing the internal surface of the rotating unit and close to the latter.

The information given by the tempcrature sensing device is transmitted to a control'device, of a type which is in itself known, for the corresponding heating element. This control device may regulate the heat output so as to produce a definite temperature in the rotating unit, or to produce a given temperature programme.

Means are advantageously provided for the thermal insulation of the shaft carrying the'rotating unit from the heating elements. For this purpose one can use an externally polished tube located between the heating elements and the shaft and/or a jacket of insulating material, for example asbestos, refractory cement, or diatomaceous earth agglomerates.

For certain applications it is desirable to arrange several treatment zones of different temperatures on the same equipment, each temperature zone corresponding to a disc of revolution of the cover. The fixed element thus also consists of several sections, each section comprising a heating element and a sensing device, and being linked to a heating control.

In order that the invention may more readily be understood, the following description is given, merely by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal section through a heating roller according to the invention;

FIGURE 2 is a section along the line a-a of the roller of FIGURE 1;

FIGURE 3 is a section along the line bb of the roller of FIGURE 1; and

FIGURE 4 illustrates a suitable control arrangement.

According to FIGURE 1, the roller consists of a hollow steel cover 1, high gloss chromed externally, mounted on a drive shaft 2 which may be caused to rotate. The said cover 1 has externally the shape of a cylinder whose axis coincides with the axis of rotation of the drive shaft. The external diameter of the cover is 162 mm. and its length 310 mm. The thickness of the cover, in the part which is used, is 4 mm.

Two annular electrical resistances 3 and 4, cast in bronze, are affixed to a stationary portion or support 5 of the machine. The radial play between the external periphery of the resistances and the internal cylindrical surface of the cover is about 1.5 mm. The heating capacity of resistance 3 is about 1100 w., and that of resistance 4 about 650 w., the elements being partannular in cross-section (FIGURES 2 and 3). The heating zone extends over a sector of 240", with the part 6 of the annular ring being formed from a. heat insulant consisting of diatomaceous earth agglomerate.

The drive shaft 2 is thermally insulated from the resistances 3 and 4 by a diatomaceous earth insulant 7 and a steel tube 8.

The emissive surface of the resistances facing the internal surface of the cover consists of stripes which gives that surface a total emission factor close to that of a black body.

The internal face of the cover is lined with a matt black commercially available paint, which confers to that surface a total emission factor of about 0.95.

Two thermistors 9 and 10, positioned at the surface of the diatomaceous earth zone 6, one being in section a-a and the other in section b-b, allow the heating to be controlled. These thermistors are located at the centre of the unheated zone 6, so as to be as sensitive as possible to the radiation emitted by the cover 1. These thermistors are linked to amplifiers 13, 14 (FIGURE 4) which provide the heating control of resistances 3 and 4, in a manner which is in itself known.

Two thermocouples 11 and 12 are placed alongside the thermistors 9 and and are linked to a temperature recorder 15.

Given that firstly the total emission factor of the resistances is close to that of a black body and secondly that the cover has an internal surface whose absorbing properties are very close to those of a black body whilst being externally polished so as to radiate as little heat as possible, the temperature of the cover is very close to that of the resistances. These characteristics reduce the heat losses and allow better temperature control. For example, using the apparatus of the invention described, it was possible to control the external temperature of the cover to 220 C. when the temperature measured at 11 inside the cover was 240 C. Equally it proved possible to generate two temperature zones in the cover, one at 130 C. at the position of resistance 3 and the other at 220 C. at the position of resistance 4, when the temperatures measured inside the cover were 138 C. at 11 and 240 C. at 12.

By way of comparison, a device similar to that described above was used, but with the internal surface of the cover not coated with a lining such as that described above. In order to obtain a temperature of 220 C. as before, at the surface of the cover, the temperature measured at 11 inside the cover had to be raised to 405 C.

According to the example described above, the heating zone of the resistance extends through a sector of 240 and a thermal insulant extends through a sector of 120.

It is to be understood that the angle of the sector containing the thermal insulant may be varied. In practice, good results are obtained if this angle is between 15 and 180.

The thermistors described in the above example are commercially available thermistors. It is for example possible to use thermistors in vacuum tubes made of glass which is transparent to infra-red.

The good heat transmission characteristics and the control in the example described allow the external temperature of the cover to be controlled to :0.S C. over the temperature range of to 220 C. It is obvious that the temperature range depends on the heat treatment carried out and on the characteristics of the fibres to be treated, and does not in any way limit the range of the invention described above.

The apparatus described assures simple and precise temperature measurement in any zone of the rotating unit and as a result allows simple and precise control of the temperature envisaged. Equally, it easily makes it possible to generate several temperature zones in the roller by juxtaposition of various fixed elements.

Furthermore, it makes it possible significantly to improve the heat transmission between the heating element and the rotating unit and this has numerous advantages:

(a) The heat treatment output is improved.

(b) Since the radiating surfaces of the heating element and of the rotating unit have high coefficients of emission, it is no longer necessary to have only very slight play between the two surfaces, and this considerably simplifies the construction of the equipment.

(0) The temperature difference between the heating element and the rotating unit is substantially reduced, and this assists the precision of temperature control of the rotating unit.

We claim:

1. A heating roller assembly comprising in combination:

(a) a hollow cover, rotatable about an axis;

(b) internal and external surfaces to said cover, said internal surface having a total emission factor close to that of a black body;

(0) a fixed member located inside said cover;

(d) an external surface to said member closely adjacent but spaced inwardly from said cover internal surface, so as not to touch said cover internal surface, said fixed member external surface having an emission factor close to that of a black body;

(e) a heating element forming part of said fixed member;

(f) a temperature sensitive device, which is sensitive to heat radiation, located in said external surface of said fixed member, but thermally insulated from said heating element; and

(g) control means controlling the heat of the heating element responsive to the temperature sensed by the temperature sensitive device.

2. The heating roller assembly specified in claim 1, wherein said cover is mounted for rotation on a drive shaft, said shaft passing through said fixed member, and further insulating means positioned between said heating element and said drive shaft.

3. The heating roller assembly specified in claim 1, wherein said temperature sensitive device comprises at least one thermistor.

4. The heating roller assembly specified in claim 1, in which said fixed member comprises a plurality of slabs disposed axially adjacent one another, within said cover, each said slab including a heating element and a temperature sensitive device, which is sensitive to heat radiation, and means for controlling the heating of each said heating element responsive to the temperature sensed by the temperature sensitive device associated therewith.

(References 011 following page) References Cited UNITED STATES PATENTS Bremer et a1. 219-464 X Barlow et a1 219469 Van Toorn 219-470 Johnson 219-469 X 3,310,655 3/1967 Hager 219-470 3,369,106 2/1968 Troll 219469 X RICHARD M. WOOD, Primary Examiner. 

